I need help understanding saltatory conduction in nerve fibers. I understand how an action potential functions at a local node, but I don't fully understand how that event directly triggers the action potential at the next node. Are the ion channels at each node triggered (1) directly by electromagnetic fluctuations resulting from a transverse current across the membrane at the previous node, or (2) are they triggered by the longitudinal flow of ions within the axon resulting from voltage differences between nodes (also resulting from flow of ions across membrane)? Can anyone help explain this to me?